Just make something like this in your game folder:
Game Folder
>ReShade Folder
>>Presets Folder
>>>Default.ini
>>Screenshots Folder
>>Shaders Folder
>>Textures Folder

At least that's how I like to organize things, remember that you can manually edit the configuration file for your specific game at "%appdata%\ReShade\game.ini"
I still find the interface for creating these things a bit lacking.

So to sum it up:
>create "ReShade" folder inside your game folder
>create "Presets", "Screenshots", "Shaders" and "Textures" folders
>create "Default.ini" (or really whatever you want to name it, extension isn't even required afaik)
>write the full paths of folders and the preset in the config file or at the ReShade 3.0 GUI

With 3.0 I placed ReShade32.dll and ReShade64.dll in "C:\Program Files (x86)\ReShade" and then I extracted the downloaded .zip version of the shaders from
github.com/crosire/reshade-shaders to that same folder (Resulting in a Shaders and Textures subfolder.) you can then optionally open the shader files and set your preferred default values directly or skip this and then use the in-game UI of ReShade 3.0 itself.

When "installing" ReShade 3.0 I simply copied ReShade32.dll and ReShade64.dll to a known compatible game and started it resulting in the creation of the settings files.

I then quit the game and copied the settings files back to the main ReShade folder.

ReShade.ini (or Default.ini if you want to use that.) looks like this:

And ReShade_Settings.ini (Set up in the above file under the Preset= path.) looks like this:

[GLOBAL]
Techniques=SMAA,

Can also contain shader specific settings but I only use it to pre-enable the shaders I want to use with the games I use ReShade which with the current selection of 3.0 compatible shaders is primarily just SMAA itself so for me using a single path for everything works pretty well.
(The SMAA shader file itself is lightly customized with the default settings I want to use otherwise most of those can be defined in the preset ini file as well if you use the in-game config which will save those settings to it.)

For the rest of the games I use ReShade with I simply now just copy over the ReShade.ini settings file along with ReShade32 and ReShade64 .dll and rename the appropriate one to whatever API the game is using which is generally D3D9.dll or DXGI.dll

If needed (In for example Witcher 3 for one example or GTA V for another.) these settings in ReShade.ini can be modified further.

"PreprocessorDefinitions="

Generally by setting logarithmic and inverted for proper depth buffer detection although this is primarily for effects like depth of field or ambient occlusion and any upcoming 3.0 compatible shader requiring depth buffer detection to work properly.

luluco250 wrote: I still find the interface for creating these things a bit lacking.

It is indeed lacking, but I wasn't able to come up with a better structure that is reasonably easy to implement (a full file browser for instance is a bit of work, for which I don't have the time at the moment). I'm always open for suggestions here, so if anybody has ideas, please do not hesitate to post them!!